Miniturized E-Shaped Dual Band PIFA on FR4 Substrates

A novel design of compact planar inverted F-antenna (PIFA) is proposed for dual band resonant frequencies. The antenna is designed and fabricated on FR4 cheap substrates with dielectric constants epsiv_r=4.7, respectively. Over 95% reduction in the antenna size is achieved from conventional lambda₀/4 rectangular PIFA resonating at same frequencies. This is done by implementing two oppositely shorting capacitive straps under the radiating surface. Dual band operation is achieved by inserting two parallel slots on the edges of the PIFA radiating surface forming an E-shape. In this case, the center wing resonates at the higher frequency while the two side wings resonate at the lower frequency. The antenna resonance frequencies on FR4 substrate are 1.07 GHz and 2.77 GHz with areas´ reduction ratios of 97% and 81% for the lower and upper resonance frequencies, respectively. The antenna size on FR4 substrate is 13times11times8 mm³. The antenna directivity is 3.73 with radiation efficiency 97%. The radiation pattern has acceptable shape with low cross polarization in both resonances and at both E-plane and H-plane directions